Apple has confessed that some iPhone 6Ses have worse battery life than others because their processors are made by two different chip bakers.

The Cupertino giant said in a statement on Thursday that the handsets using TSMC-built 16nm A9 processors will have a slightly longer battery life than those powered by Samsung-built 14nm A9 CPUs, but that the difference is far smaller than what had previously been suggested.

That's right – the chips with the larger transistors (TSMC's 16nm gates) last longer per battery charge than the smaller ones (Samsung's 14nm gates).

Typically, hardware makers shrink the transistor gate size so they can ramp up clock speed and performance without drawing too much more current to switch the gates on and off.

But the smaller you go, the more current you leak when the gates aren't doing anything, unless you use mitigating technology like FinFET designs. Samsung's shrink to 14nm just isn't working out as well as TSMC's 16nm parts.

This tool can identify whether you have a TSMC or a Samsung-built brain in your iPhone.

"Our testing and customer data show the actual battery life of the iPhone 6s and iPhone 6s Plus, even taking into account variable component differences, varies within just 2-3 per cent of each other," an Apple spokesperson said today.

Shortly after the first iPhone 6S and 6S Plus handsets hit the market, silicon-studying researchers discovered that two different companies were manufacturing the A9 CPU used by the handset. Otherwise-identical phones were found to be powered by either a TSMC or Samsung 64-bit ARMv8-compatible chip, and the two processors were fabricated using different techniques.

More recently, variousestimates suggested the difference between the two could be as much as seven per cent, with TSMC chips providing a longer battery life for the iPhone 6S than their Samsung counter parts.

Apple's statement confirms there is indeed a difference in the battery life between the two CPUs, but nowhere near what was being reported.

"Certain manufactured lab tests which run the processors with a continuous heavy workload until the battery depletes are not representative of real-world usage, since they spend an unrealistic amount of time at the highest CPU performance state," sniffed Apple.

"It's a misleading way to measure real-world battery life."

While the difference in battery life may indeed be virtually negligible in the wild, the speculation could also be enough to turn Apple off its two-manufacturer approach and go with a single processor manufacturer to handle all of the CPUs for future iPhone and iPad releases. ®

Reminder to conspiracy theorists: Samsung's electronics wing makes Android smartphones and tablets that rival Apple's iThings, while its semiconductor arm makes the chips in Apple gear. One to think about.